Toyota Denso 89661 Immo Off and Immo Reset Dumps: Hilux, Corolla, Yaris and RAV4

A 2008 Hilux 2.5 D-4D comes in on a trailer: the owner lost both keys, a locksmith couldn’t get a key to register, and someone has already tried a used engine ECU that made things worse. The label on the ECU starts 89661. Every Toyota engine ECU does, and the digits after the dash tell you the model and the variant. The question for you is whether the immobiliser data on this ECU can be reset so new keys can be learned, or whether the sane option is to switch the immobiliser off in the ECU altogether.

Two different files, and they’re not interchangeable

Immo reset

Toyota stores the registered transponder codes in the engine ECU on transponder-key cars (up to roughly 2010, depending on market). An immo reset dump puts that memory back into the factory registration state. With the reset written, the ECU accepts the first keys it sees and stores them, following the Toyota master-key registration procedure (ignition cycles, or Techstream on later cars). The car keeps its immobiliser. This is the file to use when the customer has lost all keys, when a used ECU refuses the car’s keys, or when a locksmith tool such as Tango, Zed-Full or AVDI reports a locked ECU.

Immo off

The ECU starts regardless of the transponder. Cheaper, faster, and it leaves the car without a factory immobiliser. Correct for a dead transponder amplifier, off-road or agricultural use, or when the reset route isn’t available for that ECU version. Tell the customer and put it on the invoice; in most EU countries the insurer expects the immobiliser to be there.

Transponder cars vs smart key cars

This is where used-ECU jobs go sideways. On a smart key Toyota (push-button start: Avensis T27, RAV4 from about 2006 with the option, later Corolla and Auris, Land Cruiser 150), the engine ECU is only one of three parts. The certification ECU (smart key module) and the ID code box hold the key data, and the engine ECU is registered to the ID code box. Resetting the engine ECU alone doesn’t give you a car that accepts keys; you either reset all three or replace them as a matched set. On those cars ask for the immo off file if the customer just needs it running, or budget for Techstream and the full re-registration.

On a plain transponder car (turn-key, chip in the key: Hilux Vigo, Yaris up to 2011, Corolla E12/E15, Avensis T25, RAV4 XA20/XA30 without smart entry), the engine ECU is the only place the key data lives, and both files do exactly what they say.

Reading the Denso ECU

Which tool reads what depends on the ECU generation, not the car:

1. Older Denso boards with an external 93C56/93C66 EEPROM: read the EEPROM on the bench with UPA, XProg or Orange5. The immo data is in there. Ten minutes.
2. 2005-onward boards with an NEC 76F00xx MCU and the data inside it: bench read with Orange5, XProg or ACDP on the MCU pads, or an OBD read with Zed-Full, AVDI or Tango on versions those tools support. Check your tool’s list first; Denso NEC support is patchy across firmware.
3. Diesel Hilux and Land Cruiser (1KD/2KD) with the Denso flash ECU: full flash read in boot mode with KTAG, FoxFlash or KT200, or OBD with KESS V2/KESS3 on supported software. The immobiliser bytes come along with the flash on most of these.

Whatever the route, keep the full read. A Toyota ECU written with a wrong-generation file is often done for.

Numbers on the label

Toyota engine ECUs are 89661-xxxxx, and the group after the dash tracks the model on most: 02 for Corolla, 0D for Yaris, 0K for Hilux, 42 for RAV4, 05 for Avensis, with the last digits for engine, gearbox and market. Two ECUs with the same first group and a different last digit are not always interchangeable, so quote the whole number when you order. The Denso catalogue also carries Nissan units listed by 23710 number, for example NISSAN NAVARA DENSO 23710-EB360 E20KU4C_ T2F2H61BA3 IMMO OFF DUMP and NISSAN PATHFINDER DENSO 23710 EB31B E20MU4C_ T2H1P61B25 IMMO OFF DUMP; the Toyota entries follow the same format with the 89661 number and the Denso board number.

Short answers

Can I reset a smart key car with just the engine ECU?

No. Engine ECU, certification ECU and ID box together, or immo off.

Used ECU with a different last digit?

Ask first. Same engine and gearbox usually works; different market codes can lock out the reset.

Send the ECU read and a clear photo of the 89661 label through the request form, say whether it’s a turn-key or push-button car, and whether you want reset or immo off. The Denso page and the Toyota brand page hold the ready-made dumps; the wider immobilizer category covers the certification ECU side.